Metallurgical vessel and supporting ring structure



July 15, 1969 L. T. CAMPBELL m METALLURGICAL VESSEL AND SUPPORTING RING STRUCTURE Filed Dec. 23, 1965 FIG. i

INVENTOR LOUIS T. CAMPBELL ATTORNEKZ United States Patent i US. Cl. 266-36 6 Claims ABSTRACT OF THE DISCLOSURE Metallurgical vessel is supported in a trunnion ring comprising a plurality of interconnected ring segments. The connections between ring segments provide for movement of the ring segments relative to one another to relieve thermal and other stresses tending to deform the ring.

This invention relates to metallurgical apparatus, and more particularly to supporting structures for converter vessels.

For many years in the metallurgical arts, particularly in the iron and steel industry, molten metal has been refined by blowing air through the metal in large, opentop converter vessels. In recent years, the oxygen steelmaking process known as the basic oxygen furnace (BOF) process has gained wide acceptance in the industry. In this process, a stream of oxygen is blown into the metal to be refined by means of a lance lowered through the open top of a basic-lined converter vessel.

Converter vessels used in the BOP process are conventionally fixedly received in a rigid trunnion or supporting ring disposed about the periphery of the vessel. A trunnion taking the form of a shaft is attached to the supporting ring on each side thereof, the trunnions ex tending to be rotatably received in bearings mounted on stanchions, which latter bear the weight of the entire assembly.

It has become the practice to dispose the supporting ring in radially spaced relationship to the conve-rtor vessel to accommodate thermal expansion of the vessel in a radial direction, to facilitate heat dissipation from the vessel, and to permit replacement of either the vessel or the supporting ring.

The rigid type of supporting ring construction discussed in the foregoing possesses the important disadvantage of short service life, being prone to early 7 failure.

Therefore, a main object of the invention is to provide an improved converter vessel supporting ring structure which overcomes the disadvantages of the prior art structures and possesses an extended service life.

In the drawings, wherein similar reference characters denote similar elements throughout the several views:

FIGURE 1 is a view in elevation of a converter vessel equipped with a supporting ring structure made according to the principles of the invention, shown suitably mounted in a BOF plant;

FIGURE 2 is a plan view of the converter and supporting ring structure of FIGURE 1; and

FIGURE 3 is a fragmentary enlarged view showing in partial vertical cross section a joint between, segments of the supporting ring structure of FIGURE 1 and 2.

As previously indicated, it has been observed that rigid support rings of the prior art tend to fail early in their service life. Failures usually occur at one of a plurality of locations in the ring that are at an angle of from about 2060 (herein designated a) from the longitudinal axes of the trunnions, as measured from extensions thereof at the center of the supporting ring.

Patented July 15, 1969 These points at which early failure would be anticipated, were the supporting ring structure of FIGURE 2 of rigidtype prior art construction, are indicated generally as points A on FIGURE 2. Points A are points at which prior art rigid rings tend to undergo deformation in bowing outwardly along the axis designated Y-Y in FIG- URE 2. The apparent reasons for such deformation are that points A become site-s of concentration of thermally-induced and other stresses and eventually, after repeated deformation, sites of early failure.

It follows that another object of the invention is to provide a novel converter vessel supporting ring structure which avoids concentration of stress which would tend to cause early failure of the ring.

The foregoing and other objects are accomplished by the invention, which can be briefly described as a converter vesel supporting ring structure which comprises a plurality of ring segments disposable annularly about the converter vessel, and means connecting the ring segments for dissipating stresses induced in the ring. While not intending to be bound by theory as to why rigid-type converter vessel supporting rings are subject to deformation and stress concentration, the reasons believed to cause such will be set forth.

To understand these reasons, it is convenient to first consider the BOP operation in its blowing phase. In this phase, intense heat is generated in the vessel by the oxidation of carbon and other elements in the molten metal by the oxygen lance. Much of this heat is transmitted through the refractory lining of the converter to the converter shell, to be dissipated therefrom largely by radiation. Since the supporting ring is disposed only a short distance away from the vessel, it will absorb much radiant heat on .its inner periphery, i.e., the surface facing the converter. This results in a thermal gradient of perhaps 300 magnitude extending from the inner to the outer periphery of the supporting ring. The inside of the ring will, accordingly, undergo more thermal expansion than the outside. This disproportionate expansion operates to straighten an arcuate, rigid supporting ring. But because of restraining forces provided by greater rigidity of the ring in the area of the trunnions and by the trunnions themselves, held by the bearings and the weight of the charged 'vessel, the stresses created by this disproportionate thermal expansion cannot be dissipated. That is to say, an equilibrium cannot be achieved by straightening of the ring. Rather, these stresses will operate to deform the ring by bowing it outwardly along an axis perpendicular to the axis of the trunnions (the Y-axis in FIGURE 2) with the bows beginning and ending in the vicinity of points A. Points A thus are sites at which the thermally induced stresses exceed their restraining forces. The metal in the ring at the ends of the bows will undergo a permanent set, having been forced beyond its elastic limit by the thermally induced stresses. These areas become the sites of concentrated thermal and other stresses, and eventually, sites of early failure.

After the blow the BOP vessel is rotated about the longitudinal axis of the trunnions to the slagging position, then to the tapping position, to pour slag and metal respectively into appropriate receptacles. During these operations, a new set of thermal conditions is introduced,

- which further contribute to the deformation of the ring outwardly along the Y-axis.

In the slagging and tapping positions, the outer side of the ring is exposed for long durations to heat radiated from molten material in the slag pot or steel ladle into which the converter vessel is discharging. This occurs at a time when no intense heat is being generated in the vessel, whereby the inner periphery of the supporting ring has an opportunity to dissipate much of its previously absorbed heat. Thus, in the slagging and tapping operations the outer side of the supporting ring tends to expand more than does the inner side, with a resultant straightening force on the ring; but again because of the restraining forces, the ring cannot straighten. The thermally induced stresses concentrate at the areas in the ring that have already undergone deformation, because the deformations have created discontinuities in the ring and stresses tend to concentrate at structural discontinuities.

It has been seeen that the normal blowing, slagging and tapping operations of a BOF vessel create areas of thermally-induced stress concentration in the supporting ring structure. To these are added certain external stresses induced in the ring in the charging phase of the BOP operation. When the vessel is rotated to the charging position, shocks resulting from impact of scrap being charged create external stress loads which are concentrated at the areas of deformation in the supporting ring structure for the same reasons that thermally induced stresses concentrate there. Thus, external stresses are superimposed on areas already under concentrated thermal stresses.

After charging, another blowing phase of the BOP operation is executed and the cycle is complete, with the thermal conditions discussed hereinabove reestablished in the ring. Thermal stresses induced in the blowing phase, in addition to operating to deform the ring, will also concentrate at the deformed areas. The entire cycle is repeated at frequent intervals in the operation of a BOF plant. Thus it is that the normal operation of a BOF vessel induces cyclically recurring concentrations of stresses in rigid converter vessel supporting ring structures and tends to cause early failure. But, irrespective of the reasons why the rigid-type supporting rings of the prior art tend to deformation and stress concentration as they do, the inventive supporting ring structure avoids early failures caused thereby.

The features, objects and advantages of the inventive converter supporting ring structure will appear most fully from the following detailed description which, when considered in connection with the accompanying drawings, discloses a preferred embodiment of the invention for purposes of illustration only and not for definition of the limits of the invention. For the purpose of determining the scope of the invention, reference may be had to the appended claims.

Referring to the drawings in greater details, a converter vessel such as is used in the BOP steel-making process is indicated at in FIGURES 1 and 2, Annularly disposed about vessel 10 is shown a trunnion or supporting ring structure made in accordance with the principles of the invention and generally indicated at 12. The vessel 10* is supported in ring 12 by brackets such as are indicated at 22, which mount the ring 12 in spaced relationship to the vessel 10 so as to define an annular gap 24 therebetween.

Trunnions 26 and 28, respectively, are secured to ring 12 and take the form of shafts extending in longitudinal axial alignment from opposite sides of the supporting ring 12. Trunnion shaft 26 is rotatably received and supported by bearings 30 and 32 which are in turn supported by stanchions 34 and 36, respectively, on suitable frame structure 38 and foundation 40. Trunnion 28 is similarly supported on the opposite side of vessel 10. Gears 42 and 43, secured to each trunnion are provided, driven by suitable means not shown, for rotation of the converter about the axis of the trunnions to its various operating positions. Tap hole 44 is provided for discharge of refined metal from the converter. The bearing assembly on one side of the converter may be advantageously made slidable along the longitudinal axis of the trunnion to accommodate variation of the supporting ring from its original diameter.

,Referring particularly to FIGURE 2, for reasons discussed hereinabove, supporting rings of the prior art have tended to bow outwardly along an axis Y that is generally normal to the longitudinal axis X of the trunnions.

As previously noted, failures in the prior art rings usually occur at points of concentrated stress indicated at A in FIGURE 2. In order to dissipate the thermal and other stresses concentrated at points A in the prior art rigid supporting rings, the supporting ring 12 is of novel con struction. In this construction, supporting ring 12 comprises four elongated, arcuate ring segments designated 14, 16, 18 and 20, respectively, disposed in end-to-end abutting relationship annularly about the vessel 10. Trunnion 26 is secured to side segment14 and trunnion 28 is secured to side segment 16. Front and back segments 18 and 20 extend to connect the side segments along the front and back respectively, of the vessel 10 to form an annular ring.

Connecting each segment to the segments adjacent thereto are means for dissipating stresses induced in the ring, indicated generally at 50 and preferably positioned at areas in the ring that had been sites of stress concentration such as points A. In the preferred embodiment shown inthe drawings, these means 50 take the form of stiff, jointed, hinged connections between segments, comprising a pin 52 inserted in vertically extending aligned apertures in the connecting segments, the ends of which are configured for hinged connection.

An illustrative embodiment of a form which a hinged connection may take is shown in FIGURE 3. In this figure, a pin 52 is shown hingedly connecting front segment 18 and side segment 14, both of which are of box girder construction. In this embodiment, front segment 18 has a means such as extension 58, seen also in FIGURE 1, for mating with an end of side segment 14. In the drawings, extension 58 is narrower than the remainder of front segment 18. Side segment 14 is provided with means for mating with the front segment 18. In the case illustrated, these means take the form of a recess 60 receiving the extension 58. Vertically extending aperture means 54 are provided in extension 58 and are adapted for alignment with aperture means 56 provided in side segment 14, for receiving pin 52 when the two segments are in mating relationship. A similar connection is provided at each juncture of a side segment with a front segment and a back segment. It is contemplated that suitable mat ing configurations for the ends of the ring segments other than those illustrated are operable in the invention.

In operation, a converter with the inventive, articulated supporting ring structure attached is placed in normal service. Incident tothe various phases of converter operation, thermally induced stresses will be established in the ring tending to straighten it. Whereas heretofore the stresses concentrated in rigid areas of the ring that eventually failed, the hinged connection provided by the inventive support ring permits the segments, particularly the front and back segments, to expand and contract under the thermal effects of converter operations and thereby dissipate thermally-induced and other stresses established in the ring.

What I claim is:

1. Metallurgical apparatus, comprising a metallurgical vessel,

a supporting ring surrounding the vessel and subject to stresses tending to deform the ring,

the supporting ring including first, second, third and fourth elongated, arcuate ring segments,

the first and second ring segments being disposed on diametrically opposite sides of the vessel,

a first trunnion operatively associated with the first ring segment and a second trunnion 'operatively associated with the second ring segment,

each trunnion having a longitudinal axis,

' the trunnionsbeing disposed in axial alignment with the'axes of the trunnions defininga rotational axis for the vessel,

, each of' the first and second ring segments having a first end portion located on a first side of the rotational axis and a second end portion located on a second side of the rotational axis opposite said first side,

the third ring segment being located on said first side of the rotational axis and having opposite first and second end portions,

the fourth ring segment being located on said second side of the rotational axis and having opposite first and second end portions,

the supporting ring including first connecting means pivotally interconnecting the first end portions of the first and third ring segments on said first side of the rotational axis,

second connecting means pivotally interconnecting the first end portion of the second ring segment and the second end portion of the third ring segment on said first side of the rotational axis,

third connecting means pivotally interconnecting the second end portions of the first and fourth ring segments on said second side of the rotational axis, and

fourth connecting means pivotally interconnecting the first end portion of the fourth ring segment and the second end portion of the second ring segment on said second side of the rotational axis,

each connecting means operating for relative movement between interconnected ring segments to relieve the stresses tending to deform the ring, and

mounting means for mounting the vessel in the supporting ring.

2. The metallurgical apparatus of claim 1,

each connecting means including means defining an aperture in each interconnected ring segment end portion,

the apertures being aligned in a direction transverse to the plane of the supporting ring, and

a pin member received in the aligned apertures.

3. The metallurgical apparatus of claim 1,

the mounting means including a plurality of bracket members spaced around the vessel,

each ring segment carrying at least one of the bracket members.

10 4. The metallurgical apparatus of claim 1, wherein the vessel is a converter.

5. The metallurgical apparatus of claim 1, each connecting means being at an angular location of from about to 60 measured from the rotational axis at the center of the supporting ring. 6. The metallurgical apparatus of claim 1, the ring segments being of generally equal length.

20 References Cited UNITED STATES PATENTS 1,042,876 10/1912 Blackwood 266-35 1,079,359 11/1913 Oppenheimer 220-33 1,088,401 2/1914 Bretaud 26636 FOREIGN PATENTS 1,293,832 4/1962 France. 1,152,717 8/1963 Germany.

J. SPENCER OVERHOLSER, Primary Examiner EUGENE MAR, Assistant Examiner 

